Polyester includes aliphatic polyesters and semi-aromatic polyesters. Poly(hydroxyalkanoic acid) (PHA), such as poly(lactic acid) (PLA) and poly(hydroxy butyrate), is an aliphatic polyester comprising renewable monomer such as production by bacterial fermentation processes or isolated from plant matter that include, but not limited to, corn, sugar beets, or sweet potatoes. There is a growing demand of or interest in such bio-based polymers such as automotive application, consumer products and as disposable packaging material.
The resin can be used for thermoformed or injection molded articles such as in automotive parts, computer housing or other electronic parts, machine parts, and packaging articles such as cups, trays, and clam shells, and automotive parts such as dash board. Under the humid and elevated temperature conditions, PHA can be susceptible to hydrolysis, which can lead to degradation of their physical properties. At high temperature, water or water vapor hydrolyzes the ester bond and initially forms carboxyl and hydroxyl end groups. The hydroxyl groups and the carboxyl end groups on the ends of the polymer chain may accelerate further hydrolysis. This behavior restricts the use of PHA. Under such conditions, the mechanical and electrical properties of PHA can be deteriorated. This may be a problem in using PHA to produce certain articles for use in applications including electronic products and auto parts, where the connectors and parts are likely to be used in a humid and high temperature environment. There is therefore a need or desire to produce such articles comprising PHA having improved hydrolytic stability.